Attachments:
arbitrary_surface.png (669.6 KB)

I'm trying to follow the example in the docs for the Volume Gradient vopsop, but having no success. The docs say this:

“For example, create a sphere and a point (with the help of the Add SOP). Connect the sphere to the IsoOffset SOP and change it to SDF. Next, connect the point and IsoOffset to the VOP SOP. In the VOP SOP, connect P in Globals to the N output using the Volume Gradient. In the viewport, the point normals will show you the direction. For it to work, the point must be located within the limits of the SDF field. Because the output yields the normalized data, it shows only the direction.”

I tried this and it shows nothing in the viewport at all. See attached file.
It seems so simple I'm not sure what I could be doing wrong here

Attachments:
volume_gradient.hipnc (49.7 KB)

Attachments:
attract_to_surface.hipnc (275.5 KB)

Oh, two things.

- You were bringing in all the cells as one big dynamic object. If you want to bring many objects from one SOP location, you need to specify which pieces of the geometry are to be considered separate physics objects. Here you should use an RBD Fractured Object to bring your cells in, and that needs the copy sop to create a group for each separate piece of geo.

- Your force was just too small to register

Attachments:
attract_to_surface_ee.hipnc (297.1 KB)

Ahh, thanks again eetu
It's a shame that the effect isn't quite what I was after
I was going to turn the spheres into FEM spheres and make them grow (somehow) so they squash up against each other. Using this force field doesn't seem to work well enough for keeping the spheres attached to the surface.

If you have any suggestions I'd love to hear them
I've attached my current scene - imagine those spheres squshing up against each other and you'll see what I'm after.

Attachments:
attract_to_surface_cells.hipnc (315.3 KB)

Attachments:
attract_to_surface_cells_ee.hipnc (408.2 KB)
attract_to_surface_cells_ee.jpg (231.5 KB)